Oil circuit breaker with two extinguishing chambers



H. FORWALD 2,855,487

OIL CIRCUIT BREAKER WITH TWO EXTINGUISHING CHAMBERS Oct. 7, 1958 FiledMarch 13, 1956' fivenzfor Ha akon Torn aid I B v WW United States PatentOIL CIRCUIT BREAKER WITH TWO EXTINGUISHING CHAMBERS Haakon Forwald,Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget,Vasteras, Sweden, a corporation of Sweden Application March 13, 1956,Serial N 0. 571,281

Claims priority, application Sweden March 14,1955

4 Claims. (Cl. 200150) The present invention relates to a conventionalhigh tension oil circuit breaker with two extinguishable chambers, whichare arranged to be connected in series by the movablecontacts and acontact bridge carrying said contacts. An important feature of theinvention is that one of the said extinguishing chambers, which isintended for heavy currents, is constructed in a known manner andpreferably consists of an extinguishing chamber containing adifferential piston actuated by the gas generated by the arc. Theextinguishing chamber, intended for low currents on the other hand, hasa hollow movable contact carried by a tubular member, which is connectedto a piston movably arranged in a cylinder, said piston tending to lowerthe fluid pressure in said cylinder during the first part of the contactmovement. During the last part of the contact movement the contacts inthe low current extinguishing chamber are separated, and anextinguishing oil stream passes between the contacts and into thecylinder through the opening in the hollow movable contact from thespace where the stationary contact is arranged. This last mentionedspace is in communication with an oil-filled space outside theextinguishing chamber. The cylinder, containing the piston, is alsothrough the opening in the movable contact, in communication with thespace outside the cylinder through a number of openings provided withcheck-valves, and through which openings the oil in the cylinder can bequickly, and with low resistance, pressed out by closing the breaker.The piston that lowers the fluid pressure may be actuated by a spring inthe opening direction, so that the operating force when opening thebreaking gap will be low. The spring is then tensioned during theclosing of the breaker.

In the breaker according to the invention an improved action isobtained, as two extinguishing chambers are connected in series, ofwhich chambers one gives the breaker good characteristics with heavycur-rents while the other gives the breaker good characteristics withlow currents. The breaking qualities of extinguishing chambers asgenerally used with a differential piston actuated by the pressure ofthe gases generated by the arc, and which pressure causes anextinguishing oil stream, depend on the value of the current to bebroken and for low currents are inadequate as the gas pressure generatedby the arc is too low for moving the differential piston. When theextinguishing chamber for heavy currents as mentioned above is combinedwith an extinguishing chamber designed for breaking low currents, acircuit breaker is obtained, which with .all currents that may occur isable to effectively extinguish the breaker are. In order to reduce thestress of the extinguishing chamber for low currents it is so arrangedthat its contacts are first separated after that the contacts of theextinguishing chamber for high currents have been separated and thebreaking arc in this chamber has normally already been extinguished. Forthis reason only occasionally an arc may occur in the extinguishingchamber designed for low currents, in which chamber at every breaking anextinguishing oil stream.

generated independently of the arc passes the breaking gap. If thepiston area, the cross-section of the opening in the movable contact andthe stroke of the piston are suitably chosen, the oil current may bemaintained during a desired time period.

The accompanying drawing illustrates one embodiment of the inventionhaving a conventional extinguishing chamber 1 of the type containing adifierential piston. This chamber is designed for heavy currents and isby means of a bridge member 3, which is fixed to the operating rod 2,connected in series with an extinguishing chamber for low currents. Themember 3 carries the movable contact 4 of the chamber 1 as well as themovable contact of the extinguishing chamber connected in seriestherewith. In the extinguishing chamber for low currents, the breakinggap 5 has a stationary contact 17 which is formed as a rod and is fixedon the insulator 18. A tubular member 19 of insulating materialsurrounds the contact 17, and is also attached to the said insulator.The cylinder 10 is attached to the lower end of the member 19. The space15 around the contact 17 is in communication with the space outside theextinguishing .chamber through openings 16. The movable contact of thebreaking gap can slide along the stationary contact and consists of anumber of spring actuated contact segments 6, which are arranged at theupper end of a tube 7, which tube at its lower end is attached to apiston 8. The movable contact 6 and the piston 8 are carried by a rod 9attached to the bridge member 3. The tube 7 extends through an openingin the wall 11 in the cylinder. Openings 14 in said wall 11 are providedwith checkvalves 13 and allow the oil in the space 12 to escape, whenthe piston 8 is moving upwardly.

The extinguishing chamber for low currents operates as follows: Atbreaking, the piston 8 and the movable contact move downwardly. Duringthe first part of this downward movement the movable contact 6 slidesalong the stationary contact 17, which projects into the tube 7.

The opening in the movable contact 6 is consequently closed by thestationary contact 17 and the fluid pressure is lowered in the space 12.A little before the end of the movement the contacts are separated andthe space 12 is thus brought into communication with the space 15through the movable hollow contact. An extinguishing oil stream thenpasses between the contacts into the space 12. When the piston 8 movesupwards the check-valves 13 allow free passage of oil from the space 12to the space 15.

I claim as my invention:

1. An oil circuit breaker comprising two are extinguishing units eachhaving a movable contact, a common conducting bridge member electricallyconnecting the said units in series, one of the said units beingdesigned to interrupt high currents and to open before the other unitwhich is designed to interrupt low currents, the last mentioned unitcomprising a stationary contact, a cylinder arranged at the outer end ofsaid contact, an annular movable contact slidable along said stationarycontact, an end wall in said cylinder, a tubular member carrying saidmovable contact and passing through the said end wall, a piston movablein said cylinder and attached to said tubular member, said end wall andpiston forming a fluid space, located between the cylinder and theannular member, said piston tending to lower the fluid pressure in thecylinder during its movement away from the stationary contact, and thesaid fluid space in said cylinder being in communication with theexterior of the cylinder through the said movable contact only duringthe last part of the I contact movement and in the open interruptingposition.

surrounding the tubular contact and within which the said pistonoperates, a cylinder end wall having an opening for the passage of thetubular contact, an annular fluid space being formed between the saidcylinder and the tubular contact and between said piston and the saidend wall, openings providing communication between the interior of thetubular contact and the said annular fluid space, so that the fluidpressure in the cylinder is reduced as the tubular contact is withdrawnfrom the fixed contact and is moved toward the open position of thecontacts, in combination with an arc extinguishing unit for highcurrents, comprising a casing and a movable contact, and a bridge memberso connecting the movable contacts of the two are extinguishing unitsfor high and low current that said units are electrically connected inseries with each other.

3. An oil circuit breaker having an arc extinguishing unit for lowcurrents, comprising a fixed contact, a movable tubular contact adaptedto slide over the fixed contact, a piston secured to the tubularcontact, a cylinder surrounding the tubular contact and within which thesaid piston operates, a cylinder end wall having an opening for thepassage of the tubular contact, an annular fluid space being formedbetween the said cylinder and the tubular contact and between saidpiston and the said end wall, openings providing communication betweenthe interior of the tubular contact and the said annular fluid space, sothat the fluid pressure in the cylinder is reduced as the tubularcontact is withdrawn from the fixed contact and is moved toward the openposition of the contacts, an insulating tubular member surrounding thefixed contact with an annular space therein for the accommodation of thetubular contact, and means whereby the said cylinder is supported fromthe lower end of said insulating member, in combination with an arcextinguishing unit for high currents, comprising a casing and a movableContact, and a bridge member so connecting the movable contacts of thetwo are extinguishing units for high and low current that said units areelectrically connected in series with each other.

4. An oil circuit breaker having an arc extinguishing unit for lowcurrents, comprising a fixed contact, a movable tubular contact adaptedto slide over the fixed contact, a piston secured to the tubularcontact, a cylinder surrounding the tubular contact and within which thesaid piston operates, a cylinder end wall having an opening for thepassage of the tubular contact, an annular fluid space being formedbetween the said cylinder and the tubular contact and between saidpiston and the said end wall, openings providing communication betweenthe interior of the tubular contact and the said annular fluid space, sothat the fluid pressure in the cylinder is reduced as the tubularcontact is withdrawn from the fixed contact and is moved toward the openposition of the contacts, and check valves in the said cylinder end Wallto permit the escape of fluid from the said annular fluid space betweenthe piston and the said wall when the movable contact is moved upwardlyonto the fixed contact, in combination with an arc extinguishing unitfor high currents, comprising a casing and a movable Contact, and abridge member so connecting the movable contacts of the two areextinguishing units for high and low current that said units areelectrically connected in series with each other.

References Cited in the file of this patent UNITED STATES PATENTS2,235,901 Ronnberg Mar. 25, 1941 2,252,983 Rossman Aug. 19, 19412,463,029 Fry Mar. 1, 1949 2,551,772 Thibaudat May 8, 1951 FOREIGNPATENTS 741,488 France Dec. 12, 1932

